Pages

Wednesday, October 5, 2016

In the last post I wrote about a variation of the BFF - Backend-for-frontend - pattern: The single-page BFF page, where the BFF does not support a full web frontend, but only a single page. The reason to use this pattern is that even BFFs can grow out of hand, at which point we can consider cutting the BFF into several single-page BFFs, each responsible for supporting just on page.

Now imagine we have a web site that uses the single-page BFF patterns extensively. As users navigate through the site and visit different pages they will in effect interact with different single-page BFFs. Each such single-page BFF is its own service, and conseqeuntly has its own host name - e.g. the frontpage BFF might be at https://frontpage.bff.ajax.com, the "my account" page might be at https://myaccount.bff.ajax.com/ and so on for each logical page on the site. Like this:

The problem we now have is that if users access these adresses - https://frontpage.bff.ajax.com, https://myaccount.bff.ajax.com etc. - we are exposing the way we have chosen to implement the system on the server side to a our users. That's bad: Users will bookmark these and then we are tied to keeping these host names alive, even if we decide to rearchitect the server side to use some other pattern than single-page BFFs. Instead I would like users to just stay of the same domain all the time - like https://www.ajax.com/ - and just visit different pages on that domain - e.g. https://www.ajax.com/ and https:/www.ajax.com/account. So how do we make ends meet? We simply set up a reverse proxy in front of the single-BFFs. Like so:

This is a standard thing to do and can easily be done with widespread technology, like nginx, squid or IIS with ARR. In other words: There is nothing new here, I am only pointing out that using the single-page BFF pattern will lead a need to set a up a reverse proxy in front of your services.